What is Hydrocolloid?

• Food hydrocolloids is a range of polysaccharides and proteins, also known as 'water soluble gum', 'gum', 'stabilisers'.
• Primary functions: Thickening agents, Gelling or texturizing agents.
• Secondary functions: Stabilisation of emulsions, suspension of particulates, control of crystallisation, encapsulation, formation of film.
• Usage levels < 2%

Factors affect gum properties

• molecular weight
• monosaccharide composition
• type of chains
• number of side chains
• distribution of side chains

Main classes of hydrocolloids

• derivatives from exudation or sap of trees (e.g. cellulose, gum arabic, gum karaya, gum ghatti, gum tragacanth)
• extract from seed (e.g. guar gum, LBG, tara gum, tamarind gum)
• extract from seaweeds (e.g. agar, carrageenan)
• microbial gums (e.g. xanthan, dextrun,curdlan)
• extract from tubers (e.g. konjac)
• extract from plant parts (e.g. starch, pectin, cellulose)

- Main hydrocolloids - Gelling agent

Thermoreversible gelling agents

1. gelatin
2. agar
3. kappa carrageenan
4. iota carrageena
5. low methoxy (LM) pectin
6. gellan gum
7. methyl cellulose and hydroxypropyl cellulose
8. xanthan gum and locust bean gum or konjac mannan

Thermally irreversible gelling agents

1. alginate
2. high methoxyl (HM) pectin
3. konjac mannan
4. locust bean gum

Pectin

• derived from peel of citrus fruits, apple pomace, sugar beet, sunflower heads.
• primarily in the form of protopectin
• types of pectin---High methoxyl pectin (HMP), DE> 50% and Low methoxyl pectin (LMP), DE< 50%

- High methoxyl pectin (HMP)

• DE---58% to 75%
• to form gel, soluble solid content 55-85%, pH 2.8-3.8. (e.g. jam and jellies)
• ultrarapid/rapid set (DE as high as 77)---used in jam with whole fruits, to ensure uniform distribution of fruits particles.
• slow set (DE~58) ---used in very acid fruits such as blackcurrant to avoid premature gelation.

- Low methoxyl pectin (LMP)

• two sub-groups---Conventional low methoxyl pectin (LMP) and Amidated low methoxyl pectin (ALMP).
• form gels in presence of calcium ions, low soluble solid content, wide pH range (1-7). Soluble solid can up to 85%.
• LMP - less calcium ion reactive than ALMP---used as thickening agent in yogurt fruits.
• ALMP - very calcium ion reactive---used in low sugar fruits preparatuin (e.g. low-sugar jam and jellies).

Carrageenan

- Carrageenan is a highly refined extract of seaweed from the rhodophyta family.
- Chemically its composition is a long chain of galactose residues linked, resulting in a long chain of high molecular weight.
a) Iota carrageenan - It is extracted from Eucheuma Spinosum seaweed.
b) Lambda carrageenan - It is extracted from Gigartina, Iriadeae and Chondrus crispus seaweed.
c) Kappa carrageenan - It is a extracted from Eucheuma cottonii and from Chondrus crispus seaweed.
- There are a few examples food applications for carrageenan:

• water dessert gels: used in gelation
• chocolate milk: used in suspension and mouthfeel
• ice cream: used in wheying off prevention and control meltdown

Alginate

• derived from brown seaweed ( Laminaria hyperborea)
• made up of blocks of D-mannuronic acid (M-blocks) and L-glucuronic acid (G-blocks)
• can form gel in presence of calcium ion in cold water; the gels is thermo-irreversible
• provide excellent stabilizing effects in frozen products. (e.g. ice-cream)
• act as thickeners and stabilizers in beverages (e.g. dry mix fruit drinks)
• propylene glycol alginate with emulsification property, used as stabilizer in emulsion (e.g. mayonnaise)

Gum Arabic

• derived from Acacia senegal L
• dissolve easily in hot/cold water
• least viscous and most soluble of all hydrocollods-up to 55%solid concentration can be used
• uses of gum arabic:
  • to retard sugar crystallization & to promote emulsification
  • encapsulation agent to encapsulate volatile flavour compounds
  • promoting stabilisation in beer foam
  • emulsifying agent and stabilizer in soft drinks

Locust Bean Gum (LBG)

• derived from seed of carob bean ( Ceratonia siliqua)
• insoluble in cold water, must be heated to dissolve-max viscosity develop when heated to~95 degree celcius, then cooled
• does not form gel by itself but form gel when combined with xanthan gum
• primary functions: thickening, stabilization of emulsions, inhibition of syneresis
• used in canned foods, sauces, desserts, ice-cream, processed meat

Guar Gum

• more highly substituted than LBG, more soluble, hydrates fully in cold water giving high viscosity
  

  

• non-gelling---used as viscosity builder, stabilizer, water binder

• very stable from pH 4-10

Xanthan Gum

• produced from fermentation of CHO substrate with Xanthomonas campestris
• completely soluble in cold water, produce high viscosity at low concentration

• excellent stability to heat and pH
• viscosity remain unchanged across temperature range (0-100 degree celcius), pH 1-13
• used as a thickening, suspending and stabilizing agents.

Cellulose Derivatives

• chemically modified cellulose
• alkaline treatment converts cellulose into ether
• examples---carboxymethylcellulose (CMC), hydroxypropylmethylcellulose (HPMC)
• very clear solution, stable over pH 4-10
• used as thickener, suspending and stabilizing agents. Modify flow characteristics.
• used in fried foods---create a barrier to oil absorption, retard loss of moisture, improve adhesion of batter.

Relative Ranking of Gum Properties

1. solution claity
2. solubility at various temperature
3. gelling vs thickening
4. suspension ability
5. "natural" vs "not natural"
6. ability to tabilize protein at low pH
7. acid stability
8. relative cost per unit weight

Gelatin

• high MW polypeptide derived from collagen by acid or alkali treatment
• 2 types of gelatin:
  • Type A : derived from acid processed materials,primarily porkskin
  • type B : derived from alkaline or lime processed materials,primarily cattle or calf hides and ossein
• rich in proline & hyroxyproline which contributes to the gelling ability of gelatin
• used in gelled jelly, yogurt, fruit iuices, top quality ice-cream and frozen produts, gummy bears, etc

-functional properties

• gel formation
• water binding
• texturizing
• thickening
• emulsion formation anfd stabilisation
• foam formation and stabilisation
• film formation
• adhesion/cohesion
• protective colloidal function